Hey there! :3

Firstly, terrain. As far as it goes, your terrain is actually quite nice. I would, however, recommend not making the spheres totally out of dirt - have a more adventurous block type. I'd also not make them complete spheres, have a more interesting shape! Many people, when they make floating islands, like to make it look like a chunk of land is missing from the ground - maybe you could do that too?
Not sure what the obsidian floor is, but if it's meant to replicate something like space, I'd use multiple blocks instead of just one - try coal blocks/stained glass etc.

Secondly, organics. I actually really like your custom flowers! Especially the pink one on the top island :3 However, I'm not sure the redstone blocks are really working for the other one; It's a bit too contrasted.
I think, also, the obsidian creatures (not too sure what they are, sorry!) don't fit well on this plot. If you want an organic like that, you'll need a lot more block types. I'd recommend making something that actually exists too - would add more relevance to the plot.

Lastly, structure - you have none. You need structure on your plot before you rank!

Good luck!
- Dutty :3